Thread: 250mW LASER stuck on
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12-07-2009 #5
To follow up this comment...
A FET is charge driven not voltage driven, the gate is a capacitor. The FET turns on when the gate charge exceeds a specific amount and off when that charge is depleted below a certain limit. Charge = current x time so to turn the FET on you need to pump enough charge in which means charging the gate capacitor. The datasheets helpfully give the charge required, in this case about 3.5 nanoCoulumb (nC) which means a pulse of about 1uS and 3.5mA will turn it on, and similarly a 3.5mA current should turn it off in about the same time. The actual gate voltage is not critical, its only needed to drive sufficient current into the gate capacitor and to maintain the charge as it leaks away.
Long and short of it is that a Bob output, buffered or not, should easily be able to drive and sink sufficient current to turn the FET on or off.
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